The invention relates to a method for connecting a supply conductor wire to a contact plate in accordance with the preamble of patent claim 1.
I. Prior Art
A method of this type is disclosed, for example, in German Laid-Open Specification DE 198 52 396 A1. This laid-open specification describes a lamp-cap contact plate with a bore for a supply conductor wire, which is welded or soldered to the lamp-cap contact plate. The bore is surrounded by a torn collar which is used to produce the welded or soldered join to the supply conductor wire.
II. Summary of the Invention
The object of the invention is to provide, for electric lamps, a method for connecting the supply conductor wire to a contact plate which, without using lead-containing solder, ensures a secure join and good electrical contact between the contact plate and the supply conductor wire.
In a method of the generic type, this object is achieved by the characterizing features of patent claim 1. Particularly advantageous features of the invention are disclosed in the subclaims.
According to the inventive method, an additional wire is used to connect the supply conductor wire which has been guided through the aperture in the contact plate to the contact plate of the lamp, an arc being generated between the additional wire and the supply conductor wire or between the additional wire and the contact plate, in the region of the aperture, so that at least some of the material of the additional wire is melted and the aperture is closed off with the aid of the molten material. This ensures that the supply conductor wire is embedded in the resolidified molten material. The solidified molten material produces a secure join and electrical contact between the supply conductor wire and the contact plate. The soldering process according to the invention only requires a short time, does not need any preheating of the parts which are to be soldered and therefore also does not lead to overheating and destruction of the ceramic or glass insulator arranged in the lamp cap.
The arc for soldering the supply conductor wire to the contact plate is advantageously generated with the aid of an electric voltage, the polarity of which is such that the positive pole is connected to the additional wire and the negative pole is connected to the contact plate and/or the supply conductor wire. In this way, the additional wire, in the discharge which generates the arc, acts as an anode, and the contact plate and/or the supply conductor wire acts as a cathode. Therefore, the additional wire is heated to a greater extent in the arc than the contact plate or the supply conductor wire. Moreover, this polarity of the electric voltage removes any contaminants from the contact plate formed during the capping of the lamp from the arc. Advantageously, the negative pole of the voltage source is connected to the contact plate, and the contact plate is in electrical contact with the supply conductor wire during the arc soldering, since the contact plate, unlike the supply conductor wire, most of which runs inside the lamp cap, is readily accessible from the outside. In this case, the arc is nevertheless preferentially formed between the additional wire and the supply conductor wire.
The additional wire advantageously consists of a material whose melting temperature is lower than the melting temperature of the contact plate, in order to ensure that the material of the additional wire is preferentially melted. However, even if the additional wire consists of the same material as the contact plate or the supply conductor wire, the above-described polarity of the electric voltage which generates the arc ensures that the additional wire is heated to a greater extent than the contact plate and the supply conductor wire, so that even in this case the material of the additional wire is preferentially melted during the arc soldering process. The soldering method according to the invention, i.e. the generation of the arc, is advantageously carried out under an inert-gas atmosphere, in order to avoid scaling of the contact plate and undesirable oxidation processes at the location of the solder.
The diameter of the aperture in the contact plate is advantageously smaller than the sum of the diameters of the supply conductor wire and the additional wire. This prevents the additional wire, during the generation of the arc, from inadvertently being introduced into the aperture, so that an undefined arc is formed, leading to an interruption to the soldering operation. The method according to the invention has proven particularly advantageous for supply conductor wires which consist of a material selected from the group consisting of copper, nickel, copper alloy or nickel alloy. The additional wire advantageously consists of copper or a copper alloy. The contact plate used is advantageously a metal plate which consists of a material selected from the group consisting of stainless steel, brass, copper or nickel. The method according to the invention is particularly suitable for the production of corrosion-resistant copper-nickel welded or soldered joins.